Prevent Visual Studio from trying to load symbols for a particular DLL

I have Visual Studio 2005 set up to use Microsoft's symbol servers. I also have UltraMon installed, which injects a hook DLL into every process. Whenever I start debugging my MFC application, Visual Studio says:

"Loading symbols for C:\Program Files\UltraMon\RTSUltraMonHookX32.dll..."

for anything from the blink of an eye to several tens of seconds. It's never going to find those symbols... Can I tell it not to bother looking?

(I tried creating an empty RTSUltraMonHookX32.pdb file, but Visual Studio sees that it's not good and carries on looking.)

You can't do this in a very fine grained fashion but you can disable automatic symbol loading and then manually choose the symbols to load via the Modules window (Debug -> Windows -> Modules).

To Disable Automatic Symbol loading

• Tools -> Options -> Debugging -> Symbols
• Check "Search the above locations only when symbols are loaded manually"

Also check that you have no "_NT_SYMBOL_PATH" environment variable. If you have this var symbols will load regardless of VS settings.

From Visual Studio 2010 onwards, you can go to:

Tools -> Options -> Debugging -> Symbols -> Specify excluded modules

and enter the list of the dlls which take too long to load. I use the full path, given by the Output Window; maybe it accepts wildcards or simple file names.

In my case it was because I had set "Enable .Net Source Stepping" to true in

Tools > Options > Debugging > General. 

Rather than setting it to false, I set "Enable Just My Code" to true which automatically set "Enable .Net Source Stepping" to false. It gave me a warning before doing so:

Enabling Just my code automatically disabled .Net framework source stepping

Which suggests Just My Code and .Net source stepping are mutually exclusive.

I hope this helps someone.

If you go to Debug Options -> Symbols and then check "load only specified symbols" , it won't load symbols automatically and the debugger works without problem.

You can also set up symbol server exclusions which will not be attempted to download in HKEY_CURRENT_USER\Software\Microsoft\Symbol Server\Exclusions or possibly also HKEY_LOCAL_MACHINE\Software\Microsoft\Symbol Server\Exclusions or via a .ini file at %WINDIR%\system32\inetsrv\Symsrv.ini (use the header [exclusions] and put each exclusion on its own line). The exclusions are simple pattern matches, so use msxml5.* for example.

Not only the _NT_SYMBOL_PATH can cause this behavior, but for me it was the _NT_ALT_SYMBOL_PATH environment variable that was causing the delays.

(I believe I added this variable when experimenting with WinDbg)

In Visual Studio 2013 Pro, if the Microsoft Symbol Server is checked, VS will attempt to load all symbols on their server, causing a lot of extra time.

• Load all symbol packages from MS website manually, put them on a SSD drive for speed :-)
• If you have a "_NT_SYMBOL_PATH" environment variable, remove the part "http://msdl.microsoft.com/download/symbols" from "SRVe:\symbols*http://msdl.microsoft.com/download/symbols";, so you have only the symbol path where your symbols live preciously downloaded.
• Now you have support for symbols but they wont be downloaded from MS, but loaded from drive